See the paper that was just released by Nature Geoscience!
See the paper that was just released by Nature Geoscience!
Post by Scott Jasechko, University of Calgary
Groundwater is the world’s largest family of fresh and unfrozen water, and its members range from young to old. There are toddler groundwaters recharged more recently than the year ~1960. Our earlier research showed that these modern groundwaters make up only a small share of global groundwater stocks (Ref. 1 and Water Canada).
But what of ancient ‘fossil’ groundwater—defined as groundwater that first moved under the ground more than 12,000 years ago, before the current “Holocene” time period began?
Many studies have discovered fossil groundwaters (Refs. 2-7). These ancient groundwaters may have first become isolated under the ground during one of the ice ages (~12,000 to 2.6 million years ago), or when dinosaurs wandered the planet (230 to 65 million years ago), or even before complex multicellular life evolved (e.g., more than 1 billion years ago).
Our research shows that fossil groundwaters are widespread, based on a compilation of groundwater radiocarbon, which is common in young groundwaters but less common in fossil groundwaters.
Our recent work (Ref. 8) has two main findings:
First, we show that fossil groundwater likely makes up most of the fresh and unfrozen water on planet Earth. Fossil groundwater is common at depths deeper than ~250 meters below the ground. Our finding highlights that most aquifers take a long time to be flushed, implying that most groundwater is not rejuvenated at time scales that are consistent with water management timeframes (~decades).
Second, we show that many deep well waters that are dominated by fossil groundwater also contain some modern groundwater. That is, fossil well waters are often mixed up with recent rain and snowmelt. Because some human activities pollute recent rain and snowmelt, our finding implies that deep wells are not immune to the impacts of modern-day land uses on water quality.
Back to our family analogy – our two main findings are: (i) ‘groundwater grandparents’ (i.e., fossil water) make up most of the global groundwater family (lots of grandparents, only a few grandchildren), however, (ii) groundwater youngsters (less than ~50 years in their age), are often found to hang out at deep depths with groundwater grandparents. Once in a while, youngsters may carry the consequences of bad modern habits (i.e. contamination) down to the deep depths where the groundwater grandparents live, sullying deep groundwaters once considered immune to modern contamination.
1) Gleeson T, Befus K, Jasechko S, Luijendijk E, Cardenas MB (2016) The global volume and distribution of modern groundwater. Nature Geoscience, 9, 161-168. http://www.nature.com/ngeo/journal/v9/n2/full/ngeo2590.html
2) Thatcher L, Rubin M, Brown GF (1961) Dating desert groundwater. Science 134, 105-106. http://science.sciencemag.org/content/134/3472/105
3) Edmunds WM, Wright EP (1979) Groundwater recharge and palaeoclimate in the Sirte and Kufra basins, Libya. Journal of Hydrology 40, 215-241. www.sciencedirect.com/science/article/pii/0022169479900325
4) Phillips FM, Peeters LA, Tansey MK, Davis SN (1986). Paleoclimatic inferences from an isotopic investigation of groundwater in the central San Juan Basin, New Mexico. Quaternary Research 26, 179-193. http://www.sciencedirect.com/science/article/pii/0033589486901031
5) Remenda VH, Cherry JA, Edwards TWD (1994). Isotopic composition of old ground water from Lake Agassiz: implications for late Pleistocene climate. Science, 266, 1975-1978. science.sciencemag.org/content/266/5193/1975
6) Sturchio NC et al. (2004) One million year old groundwater in the Sahara revealed by krypton-81 and chlorine-36. Geophysical Research Letters 31, L05503. onlinelibrary.wiley.com/doi/10.1029/2003GL019234/full
7) Holland G, Sherwood Lollar B, Li L, Lacrampe-Couloume G, Slater GF, Ballentine CJ (2013) Deep fracture fluids isolated in the crust since the Precambrian era. Nature 497, 357-360. http://www.nature.com/nature/journal/v497/n7449/full/nature12127.html
8) Jasechko S, Perrone D, Befus KM, Cardenas MB, Ferguson G, Gleeson T, Luijenjijk E, McDonnell JJ, Taylor RG, Wada Y, Kirchner JW (2017) Global aquifers dominated by fossil groundwaters but wells vulnerable to modern contamination. Nature Geoscience doi:10.1038/ngeo2943.
Post by Kevin Befus, University of Wyoming
I don’t mean to get your hopes up, but keep them up there. I’m not talking about recording the sonorific excitement that is groundwater flow. And, I’m not talking about the squeak of a pump handle, the gurgling of a spring, the grumble of a generator, or the roar of a drill rig. Rather, I want to share with you some songs that reference groundwater in one capacity or another, though references to specific capacity have yet to be found. Groundwater might not be photogenic …more discussion to follow, but is it musical?
For the last couple of years, I have been amassing a playlist of songs that reference water (well, ever since I discovered how perfect “Once in a Lifetime” by the Talking Heads was for motivating me during graduate school…in my opinion, there is no better song to listen to before hitting submit on that manuscript or grant for good scientific mojo). Sifting through a couple hundred songs that sometimes only marginally use water to metaphorize the human condition, I have honed the list to an ordered version of what I consider “The best/only groundwater songs”:
1) Once in a lifetime – Talking Heads
See previous post for a thorough run down
2) Water of Love – Dire Straits
A yearning for water/love, deep underground and hard to find. Let’s hope for some recharge to elevate the water table and maybe even support the river’s running free.
3) Cold Water – Old Time Relijun
Warning, this song is different, but it is about groundwater and wonderfully so. “Cold water going down…through the roots, through the mud, through the rocks, through the ground, through the sand, through the Earth and all the land”. Talk about groundwater flow and potential recharge! It’s also cold, fitting the gross expectation that groundwater near recharge areas is cooler (in regional flow systems at least) than further along the flow system.
4) I am a River – Foo Fighters
They find a groundwater system that thinks it is a river beneath a subway floor…a classic case of mistaken identity.
5) Hallelujah Band – Eilen Jewell
“I climbed down underground
to listen for a new sound
found a river underneath our feet
dark and silent, deep”
Sounds like a quiet unconfined karst groundwater system to me.
6) You Don’t Miss Your Water – Otis Redding
7) Cool Water – Sons of the Pioneers (later sung by Johnny Cash, Joni Mitchell, and others)
8) Water in a Well – Sturgill Simpson
9) Water – Jack Garratt
10) Our Lady of the Well – Jackson Browne
11) Crow Jane – Skip James (also Derek Trucks Band)
12) Well Run Dry – Phat Phunktion
My musical explorations have taught me love is like water. Groundwater? Maybe, depends on its amount, depth, and quality. Wells can be the source of good and bad waters, and we can have some say on whether it’s one or the other. These songs and others (that don’t reference groundwater specifically) bemoan or extol love/water, which comes or goes and can be so uncontrollable.
Groundwater can also be a source of contemplation. Water underground is often interpreted as “silent” (in both “Hallelujah Band” and “Once in a Lifetime”), but springs are allowed to burble and gurgle. So long as we have saturated conditions in a simple single-porosity system, I would bet the groundwater flow is generally difficult to hear. But remember, groundwater is under pressure (atmospheric, hydrostatic, or otherwise) and “wants” to break free (Queen references…couldn’t help myself), especially when in confined aquifers.
There is at least one more way groundwater systems can invoke contemplation. Back before powered pumps, drawing water from a well took time, and that time could be used to think through the triumphs and trials of life. Maybe that’s one reason why groundwater hydrologists are often excited to get into the field.
Quick aside, San Diego has recently started a music festival called GROUNDWATER, where modern house music is the theme. I have not yet sifted through their performers’ lyrics in search of water references, but I would gladly take your help. Words may be in low concentrations.
Join my musical adventures in groundwater and share your finds with us in the comments below!
For your hydrogeological musical pleasure:
feature image: IAH Netherlands Chapter
Episode 1 – A different introduction to karst
by Andreas Hartmann, Lecturer in Hydrology at the University of Freiburg
Usually, textbooks or lectures start with the theoretical background and basic knowledge of the topic they try to cover. Writing my first contribution to the Water Underground blog I want to take advantage of this less formal environment. I will introduce karst as I and many others around the world see it. As the most beautiful environment to explore and study.
Some of you may not be familiar with the term karst, its geomorphology or hydrological consequences. But I am almost certain that most of you have seen the landforms in the four pictures below.
Tower karst (1st photo) is typical of tropical regions. The picture below is taken close to Guilin, Southwest China, and I am sure many of you remember James Bond “The Man with the Golden Gun” and the beautiful tower karst islands at which parts of movie takes place (episode 3 will be a special feature about karst in the movies). Tower karst reaches heights up to 300m and often referred to by its Chinese name Fenglin or Fengcong karst, when occurring in a large number.
The 2nd photo shows the opposite landform: a huge hole in the forest ground. This is not a crater but a very big collapse sinkhole at Vermillion Creek, Northwest territories, Canada. It has an ellipse shape (60m x 120m) and 40 m below the surface, it has a lake whose depth has not yet been determined. You may not have previously heard the term sinkhole. But on the news one day you will hear stories of holes suddenly swallowing cars or entire houses in Florida or Mexico. If not due to mining, those were most probably collapses that occurred due to karstification.
The most popular features of karst are caves, some of them as large as entire buildings. The 3rd photo shows how it may look inside a karstic cave (Kalisuci Cave at Jogjakarta, Indonesia). Note that there are plenty of stalactites and that there is a lot of water that will eventually find its way back to the surface discharging a karstic spring.
The 4th photo shows the spring of the Loue River, France, which is one of the largest springs in Europe. The volumes of water coming out easily compare to the discharge of medium size rivers. If you ever saw a spring that big it must have been a karst spring!
In the Of Karst! series, I will take you on a journey through more of these amazing characteristics of karst. I will show how its evolution over time can produce the landforms shown here. I will show how karstification affects the resulting movement of water on the surface, in caves systems and in karstic rock. And I will explain why karst is so relevant for our societies. In episode 2 (late June 2017) I will speak of how karst evolves. Episode 3 (early October 2017) will a special feature about karst in James Bond other famous movies.
Last week I gave a ‘blue drinks’ presentation for a networking evening for the Victoria chapter of the Canadian Water Resources Association entitled “How much groundwater is on earth?” based on our paper from Nature Geoscience last year. Since the night was hosted at Philips Brewery, an awesome local brewery (who makes Blue Buck, the perfect blue drink, and lots of other great beer), I decided to calculate how many kegs of groundwater we have on earth or said another way “what is the volume (in kegs) of groundwater is stored on earth?”
So this blog post is a skill-testing question for all the nerds out there – answer below in the comments knowing:
a keg is 58.7 liters = 5.87e-11 km3 so there are 1.7 e+10 kegs in a km3.
Hint it is more than 1.7 e+10 kegs…. and one person during the evening got it almost correct.
Fourth year and graduate students led a fun mini-conference during class in Groundwater Hydrology (CIVE 445, Civil Engineering at University of Victoria) yesterday. Local consulting and government hydrogeologists joined, making the students both nervous and excited to be presenting to professionals with up to forty years of groundwater experience. The presentations were the culmination of a term-long independent group research project – they also write a research paper (which is peer-reviewed by their classmates). And the mini-conference culminated in beers at the grad club, unfortunately drinking beer brewed with surface water.
It seemed like a win-win-win for everyone. The students loved meeting and presenting to, and being grilled by, the people who had mapped the aquifer they were modeling or asked if their model is based on any real data. The practitioners loved seeing the new ideas and enthusiasm of the students. And I loved seeing the interaction and learning.
For any prof reading this, here is a description of the Group Research Project and the conference poster:
We hope you have a great world water day! May you sip a cool, refreshing glass of renewable groundwater and feel excited to make the world a better, more sustainable place.
by Tara Forstner, University of Victoria
I recently wrote a term paper for one of my graduate classes on the limitations of the water table fluctuation (WTF) method, and I have to say, WTF!
Techniques using groundwater level fluctuations as a means of calculating recharge are very common. With observation well hydrographs and precipitation data, this method can be applied quite simply, requiring no field work or data collection. Although, this is definitely not the method to end all recharge methods for a number of reasons. As a newbie hydrogeologist studying the WTF method, the application of the method quickly became convoluted based on its limitations and uncertainties.
My term paper focused mainly on the WTF method as described by the classic papers by Healy and Cook (2001), and Cuthbert’s novel estimation of drainage (Cuthbert, 2010) and straight line recession (Cuthbert, 2014). Here is a list of the three most important things I learned:
In closing I thought I would share one of my silly ‘WTF!?’ moments and that ‘oooooohhh’ moment that follows once I figured it out. In Healy and Cook (2002), the formula for recharge is written as R = Sy dh/dt, and later in Crosbie (2005) as R = Dh Sy and Cuthbert (2010) as R = Sy dh/dt + D. There are two things that tripped me up with this method. Firstly, the meaning of the symbols R and Dh varies slightly between papers which is easy to miss, and recharge is either calculated as a rate or a value over a specified time. Secondly, the approach in deriving the groundwater recession constant is also different in all three papers, and should be chosen on the basis of the conceptual model.
So alas, the WTF can definitely have it’s ‘WTF!?’ moments, however when the method, possibilities, and limitations are properly understood, this method has the potential of providing a cost effective and non-invasive approach in deriving recharge values.
by Matthew Currell, School of Engineering, RMIT University, Australia
As part of its recent ‘war on pollution’, the Chinese Central Government released a major policy on water pollution control and clean-up, called the ‘10-point water plan’ in 2015. The plan aims to deal once and for all with China’s chronic water quality problems. China’s water quality deficiencies became widely recognised around the turn of the millennium, following publication of seminal works by Ma Jun, Elizabeth Economy and other local and overseas environmental campaigners. It is now widely acknowledged that chronic exposure to water pollution in China has contributed to the emergence of hundreds of cancer villages, where rates of particular types of cancer that are linked to water pollution far exceed normal population-wide averages. In addition to agricultural pollution and domestic wastewater, in many regions the pollution has resulted from industries that are part of multi-national supply chains, meaning international factors have played an important role.
In a recent review paper published in Environmental Pollution, my colleague Dongmei Han and I compiled data from official Chinese government reports to provide a snapshot of the current status of water quality in China’s major river basins, coastal waters and groundwater systems, including shallow unconfined and deeper confined aquifers (Figure 1). The results are sobering, showing that despite some recent progress, about a third of China’s river monitoring stations and more than 60% of sampled groundwater wells are seriously polluted. These data agree with an internal Ministry of Water Resources report that was briefly made public in early 2016, which showed that more than 80% of the more than 2000 monitored shallow groundwater wells in northern China’s plains areas contain serious pollution and that the aquifers they monitor are unfit to supply drinking water.
In addition to the government data, we also targeted the research literature and compiled as many datasets as possible reporting concentrations of nitrate in shallow and/or deep aquifers throughout China. Compiling these data from over 70 different sources provides greater local detail about the severity of groundwater pollution (Figure 2). We chose nitrate as an ‘indicator pollutant’ because it is widely measured, easy to detect and highly water-soluble. The presence of nitrate in a sample is often an indicator that other pollutants may also be there. The results indicate that all shallow aquifers sampled contain nitrate above the typical natural background level (approximately 1 mg/L nitrate-N or 4.5 mg/L nitrate as NO3– ion), indicating some degree of pollution. Of these 36 aquifers, samples from 25 contained nitrate concentrations exceeding the US EPA maximum contaminant level (MCL) of 10 mg/L nitrate-N. Worryingly, all but one of 37 deep or karst aquifers examined contained nitrate above the background level, while 10 of these aquifers had samples above the MCL. In five of the shallow aquifers and four of the deep aquifers, median nitrate concentrations also exceeded the MCL, meaning half of all wells in the aquifer pump groundwater with nitrate levels exceeding the maximum safe level. We also compiled groundwater stable nitrogen isotope values of the nitrate where they were available. These isotope data help to identify the major sources of nitrate pollution such as chemical fertilizers, soil nitrogen, manure and domestic wastewater, as each potential source can have a unique isotope ‘signature’. Nitrogen isotopes can also provide evidence of microbes breaking down pollution; this is important when considering whether the nitrate will naturally degrade, or if engineered clean-up strategies are required.
Perhaps the issue of greatest concern from our review was the observation that in addition to being ubiquitous in shallow groundwater (as is perhaps expected in areas of intensive agriculture or wastewater pollution), nitrate pollution also frequently appears in deep wells (drilled to >100m below the surface) throughout China. Normally, the time taken for water to reach these confined aquifers is long, and much of the deep groundwater in China has been dated using radio-isotopes, which indicate that it was recharged thousands or tens of thousands of years before the present. The presence of nitrate above natural background levels in these groundwater bodies suggests that pollution is undergoing rapid ‘bypass flow’ (e.g. taking short-cuts) from the surface into deep aquifers.
The Chinese Ministry of Water Resources has made public statements indicating it believes that China’s deep aquifers are safe drinking water sources, isolated from surface pollution effects due to natural geological barriers (called ‘aquitards’ by hydrogeologists). However, our data call into question this assumption. A similar finding was recently made by a group at the Chinese Academy of Sciences, who conducted a geochemical survey of tap water from various sites around Beijing. Most of Beijing’s water supply plants pump from deep groundwater wells around the city. The survey found that a significant number of samples contained nitrate and other pollutants, consistent with our findings that contamination is reaching deep aquifers through short-cut pathways. The most likely explanation is that polluted water is flowing from shallow depths down preferential conduits, such as poorly constructed or badly maintained wells, and bypassing natural geological barriers (Figure 3).
It is estimated that over 4 million wells have been drilled in China’s northern plains alone since the groundwater boom of the 1960s and 1970s. However, only a fraction of these are registered with the government or maintained. Clearly, a program to identify and plug leaking and abandoned wells is needed to stop further pollution of China’s precious deep groundwater reserves.
We hope that our research highlights the scale of China’s water pollution challenges, and can help the public and policy makers better understand the extent and mechanisms of groundwater pollution – a problem which is causing serious human health effects. While addressing the problem of pollution in deep aquifers will be difficult, it is too important a task to ignore, as these aquifers supply drinking water to millions of Chinese people.
References & Further reading
Currell, M.J., Han, D., Chen, Z., Cartwright, I. (2012). Sustainability of groundwater usage in northern China: dependence on palaeowaters and effects on water quality, quantity and ecosystem health. Hydrological Processes 26: 4050-4066.
Currell, M.J., Han, D. (2017). The Global Drain: Why China’s water pollution problems should matter to the rest of the world. Environment: Science and Policy for Sustainable Development 59: 16-29. http://dx.doi.org/10.1080/00139157.2017.1252605
Han, D., Currell, M.J., Cao, G. (2016). Deep challenges for China’s war on water pollution. Environmental Pollution 218: 1222-1233. http://www.sciencedirect.com/science/article/pii/S0269749116310363
Peters, M., Guo Q., Strauss, H., Zhu, G. Geochemical and multiple stable isotope (N, O, S) investigation on tap and bottled water from Beijing, China. Journal of Geochemical Exploration 157: 36-51. http://www.sciencedirect.com/science/article/pii/S0375674215300030
Hydrogeologists are a diverse group, in part because we come to this discipline from so many different paths. We come from different academic programs in engineering, geological sciences and environmental sciences. These differences in backgrounds create a diversity of perspectives, which enriches hydrogeology and allows for dynamic collaborations. Engineers and geophysicists are known for bringing quantitative skills to hydrogeology, while geologists shine in problems involving stratigraphy, structural geology and embrace uncertainty. Geochemists and environmental scientists are often stronger in contaminant hydrogeology. However, each of these backgrounds also have their deficiencies. This is underscored by looking at programs in civil engineering and geology, which are two of the most common undergraduate degrees among hydrogeologists. Aside from foundational math and science courses the first years of these programs, they usually only share an elective course in hydrogeology. A review of hydrogeology courses covered by Gleeson et al. (2012) showed that aside from a few topics, these courses vary substantially in their content.
This is further complicated by how professionals are licensed in many jurisdictions, which is often based on these academic programs rather than whether someone has the capacity to practice hydrogeology. Engineers are required to have engineering fundamentals in areas such as statics, dynamics, and engineering design, along with competency is areas such as structural and transportation engineering for civil engineering. Geologists receive professional registration based on core competencies in subjects such as mineralogy, sedimentology, paleontology and structural geology. Registration for fields more closely aligned with hydrogeology, such as environmental geoscience and geological engineering may consider hydrogeology as a core requirement. In general, this means that somebody registered as a professional engineer or geoscientist might be a hydrogeologist but they also may have very little knowledge of hydrogeology. Environmental scientists and similar fields might be better prepared to practice hydrogeology in some instances but professional registration is not as common.
Maybe this involves graduate school? Many practicing hydrogeologists have advanced degrees. These programs are often designed to give a broad base in hydrogeology and typically deliver material in:
Additional material on porous media, geotechnical engineering and hydrology are frequently also covered. Anyone with a background in these areas is probably a hydrogeologist. However, there are still some grey areas. Can someone who doesn’t understand numerical models be a hydrogeologist? What about someone who has never done field work? Where to draw the line is unclear and may differ substantially based on who is asking the question. However, if the goal is to promote competent practitioners and researchers in hydrogeology, the traditional paths through engineering and geoscience may be less than ideal. The requirement of knowledge outside hydrogeology at the expense of core knowledge may be holding us back. On the other hand, a great number of us did not enter university with the goal of becoming a hydrogeologist and maybe we need these more traditional programs as gateways.